The present disclosure relates generally to high-voltage switch devices with electrostatic discharge (ESD) robustness, and more particularly to high-voltage switch devices integrated with at least one ESD protection device to improve their ESD robustness.
A high-voltage metal-oxide-semiconductor field effect transistor (MOSFET) refers normally to a MOSFET capable of sustaining a drain-to-source voltage higher than 5 volt. It can be used for load switch, voltage conversion in power management, or power amplification.
If a high-voltage MOSFET is configured to receive a high voltage from a resource external to the semiconductor chip in which the high-voltage MOS transistor is formed, the high-voltage MOS transistor should be equipped with electrostatic discharge (ESD) protection so it can withstand ESD stress caused by its external environment. ESD robustness of a device often refers to the highest ESD stress that the device can withstand without damage. A high-voltage MOSFET usually has very weak ESD robustness, substantially due to non-uniformity of electric field distribution and local current crowding effect at a discontinuous region inside the high-voltage MOSFET.
A well-known solution to improve ESD robustness of a device is to enlarge the device's size, because the maximum electric field and the current crowding effect inside the device might be reduced. Size enlargement to a high-voltage MOSFET is sometimes unfavorable, however. A high-voltage MOSFET is normally huge in size, in order to sustain high-voltage input and to provide desired driving ability. Making a huge device larger additionally requires enormous silicon area and could become less cost-effective.